Synthetic resin containers made from a synthetic resin such as polypropylene (PP) or polyethylene terephthalate (PET) have been widely put into practical use as containers for beverages. A preform that is to be formed into a synthetic resin container by blow-molding can be obtained by compression-molding by using a compression-molding machine. In executing the compression-molding, the synthetic resin in a molten state is extruded through an ejection port of a die head of an extruder and is fed to the compression-molding apparatus by a resin feeder. The compression-molding apparatus compression-molds the synthetic resin in a molten state to mold a pre-molded article and, thereafter, blow-molds the pre-molded article into a container.
The following patent document 1 discloses a method of compression-molding a pre-molded article. According to this method of compression-molding, a synthetic resin in a molten state extruded from an extrusion opening of an extruder is cut by a cutter, and the synthetic resin (bullet) after cut is conveyed to a resin-feed zone of a compression-molding apparatus. In the resin-feed zone, the synthetic resin after cut is allowed to fall down into a recessed portion that is open upward in a metal mold that is in an open state through guide means located at a predetermined guide position. Thereafter, the metal mold is closed and the synthetic resin fallen down into the recessed portion is compression-molded into a predetermined shape.
The above means for guiding the synthetic resin has an upper guide passage of an inverted conical shape of which the sectional area gradually decreases downward and a lower guide passage of an upright cylindrical shape following the upper guide passage. The lower guide passage has a sectional shape substantially the same as the sectional shape at the lower end of the upper guide passage. At the time when the synthetic resin falls down into the recessed portion of the metal mold through the guide means, the guide means is brought to a guide position where the center axes of the upper guide passage and of the lower guide passage are brought into agreement with the center axis of the recessed portion, so that the synthetic resin is brought to the central position of the recessed portion while passing through the upper guide passage and the lower guide passage of guide means.                Patent document 1: JP-A-2000-280248 (discloses positioning of a synthetic resin)        Patent document 2: JP-T-2007-508966 (discloses a metal mold including a male mold as the lower mold and a female mold as the upper mold)        Patent document 3: JP-B-6-2359 (discloses a metal mold including a male mold as the lower mold and a female mold as the upper mold)        